1. Field of the Invention
The present invention relates to small portable electronic devices such as cellular phones and mobile information devices and, more particularly, to small portable electronic devices capable of detecting the charge level of a secondary battery contained therein.
2. Description of the Related Art
Conventional small electronic devices indicate a remaining battery level by detecting the voltage of a secondary battery serving as a power source and displaying the current battery charge at several levels according to the detected battery voltage on a display mounted thereon.
Cellular phones, however, are normally kept in a bag and the like when a user is not talking on the phone, and the display of the cellular phone is thus not checked frequently. Hence, when downloading music data and so on to a cellular phone, for example, it is likely that a user keeps the operation, which takes a long time, running without noticing a decrease in a battery. This leads to a battery shortage to interrupt the data communication before the user knows it.